JP2002-181008A discloses an invention of a hydraulic control device that installs, in a valve block, a first circuit system constituted of a plurality of spool valves connected to a first pump; and a second circuit system constituted of a plurality of spool valves connected to a second pump. In the hydraulic control device of JP2002-181008A, a joining switching valve is provided, which disconnects the first circuit system from an intermediate passage. By switching this joining switching valve and disconnecting the communication between the intermediate passage and the tank, the first circuit system is joined with an arm switching valve of the second circuit system through a switch passage provided upstream of the joining switching valve.